Gas lift apparatus



April 22, 1969 B. A. ABERCROMBIE GAS LIFT APPARATUS Sheet Filed Oct. 23, 1965 INVENTOR.

.50 ////7 4. Abercramlze BY {MM/( a,,

ATI'OlP/YEKJ Sheet 2 of 2 l NV EN'TUR.

ATTOIWVEVJ A ril 22, 1969 a; A. ABERCROMBIE GAS LIFT APPARATUS Filed Oct. 23, 1965 United States Patent 3,439,626 GAS LIFT APPARATUS Bolling A. Abercrombie, Houston, Tex., assignor to Everett D. McMurry and Knud I. Brunn, both of Houston, Tex.

Filed Oct. 23, 1965, Ser. No. 503,968 Int. Cl. F04f 1/08, 1/00 U.S. Cl. 103-232 5 Claims ABSTRACT OF THE DISCLOSURE This invention relates to valves which provide for streamlined flow, which balance the sensitivity of the valve to downstream pressure upon opening, and at the same time provide for a relatively large flow capacity through the valve.

Though the valves of this invention may be useful in many different applications and environments, they have been found to have particular utility in the oil and gas industry, and particularly in the gas lift art.

It will be readily understood that, in order to produce oil or other liquids from a formation in the earth, it is customary to drill a borehole to the formation. It is also customary to connect the producing formation with receiving equipment at the earths surface by means of a string of tubing or a producing conduit. It is usually desired to install another pipe or casing around the tubing, the annulus between the tubing and casing forming a gas injection conduit. Of course, it is recognized that the annulus between the tubing and the casing might be used for the production conduit, and the annulus between the tubing and casing might be the gas injection conduit. Further, the casing might be eliminated altogether, and its function served by the borehole.

If the pressure of the producing formation is insuflicient for the flow of oil to the surface, then some artificial means are employed to aid in the production of oil from the formation. One such method is the gas lif method, by which is meant that oil is moved from the producing formation in the earth to the earths surface by the periodic injection of a gas such as air, nitrogen, or natural gas. While for safety reasons it is often preferable to employ in this operation a gas which will not support combustion in the context of its use, it will be understood that, generally speaking, any gas might be employed and thus the term gas as used herein shall not apply to any certain gas but rather shall be used for gaseous type fluids generally.

In this manner, oil is carried to the surface either continuously or in slugs by the pressurized gas, which is introduced into the gas injection conduit from a source of gas under pressure at the surface. Means are inserted at predetermined points in connection with the tubing string in order to allow the flow of this gas from the gas injection conduit into the producing conduit. It is with such means, or gas lift valves, that this invention is primarily concerned.

Any convenient number of such valves may be employed on a string of well tubing, and of course the valves Patented Apr. 22., 1969 may be used on both strings of tubing in a dual-completion well. When a plurality of valves are employed, which is the usual case, it will be generally preferred to set the individual valves so that they will open at progressively different times, thus assuring maximum efliciency of the gas lift operation.

Gas lift valves have been constructed which are sensitive to either gas injection conduit pressure, producing conduit pressure, or the differential of these two pressures on either the closing or opening cycle. For many uses, it is very much desired to limit the sensitivity of the valve to producing conduit pressure (hereinafter sometimes called tubing pressure) on opening. At the same time, however, it is desired to provide a valve with sufficient throughput capacity such that there will not be an excessive pressure drop when-adequate quantities of gas are flowing through the valve. It is also, of course, desired that the valve have a streamlined flow pattern to prevent a restriction in the flow passage. And it is also desired to provide a balancing system which is adaptable to concentric alignment and yet can be perfected without extreme attention to machine tolerances. These problems are especially acute when it is desired to provide a small outside diameter valve.

Although numerous attempts have been made to solve these problems, there is no valve presently known to applicant which provides a solution to each of these difficulties in a single valve. One valve which has been presented as a solution to these problems is a pilot valve which opens a large master valve. The pilot valve provides the small tubing sensitivity desired, and the master valve provides the large throughput capacity which is necessary. The disadvantages of this rather complex valve structure are apparent, however. For example, the pilot structure requires two separate seats and a seal ring, each of which is subject to leakage.

Another attempt which has been made to solve these difficulties provided a valve with a complex flow passage, whereby the gas was forced to turn through 270 within the valve itself, thus causing a restriction in the flow passage. The disadvantages of such a valve are readily apparent.

This invention, therefore, provides an improved valve, of particular utility in the gas lift art, which has limited sensitivity to downstream pressure on opening, has a relatively large throughput capacity, and assures streamlined flow.

In order that the manner in which the above and other objects of this invention are attained can be understood in detail, one advantageous embodiment of the invention will be described with reference to the accompanying drawings, which form a part of this specification, and wherein:

FIGURE 1 is a fragmentary, diagrammatic view of a well illustrating the method of the invention, and showing typical arrangement of apparatus in accordance with this invention in a well.

FIGURE 2 is a vertical sectional view of a valve constructed in accordance with one embodiment of this invention, illustrating the valve positioned on a string of tubing.

FIGURE 3 is a view taken along the line 33 of FIGURE 2.

FIGURE 4 is a View taken along the line 4-4 of FIGURE 3.

FIGURE 5 is a view taken along the line 5-5 of FIGURE 3.

FIGURE 6 is a view similar to FIGURE 5, but showing the valve in a closed position.

Referring now to the drawings in greater detail, a borehole 1 is illustrated drilled into the earth 2 to a producing formation 3. In the borehole 1 is positioned a casing 4, and into the casing and generally parallel therewith is tubing which is comprised of a number of sections or joints. Casing 4 and tubing 5 define a gas injection conduit 6 in the annulus between casing and tubing, and a production conduit 7 within the tubing string.

The gas injection conduit 6 is in communication at the earths surface with a suitable source of gas under pressure such as a pressure tank or compressor, generally designated 9, through means such as pipe 8.

Onto the tubing string are aflixed a plurality of gas lift valves 10 constructed in accordance with this invention. Packers 11 may be employed to seal the gas injection conduit from the lower end of the borehole.

In FIGURES 2-6 is illustrated a particular gas lift valve 10 constructed in accordance with one embodiment of this invention.

The valve 10 is held in an elongated, generally tubular, casing or housing 11 defining a valve chamber therein. In casing 11 are one or more ports affording fluid communication with the area on the exterior of the housing, such as the longitudinally extending slots 12, which are preferably parallel to the longitudinal axis of the housing. While any number of convenient ports or slots may be used, it has been found particularly desirable to include about six elongated slots equidistantly spaced around the housing 11. If the housing is about one inch in outside diameter, then such slots could conveniently be on the order of inch in width, and 1% inches in length, with the ends being tapered as indicated at 13a and 13b in order to provide for more streamlined flow. The generally tubular nature of the housing defines, of course, an inner surface and an outer surface.

On the inner surface of the casing 11 intermediate the longitudinal ends of said slots is an inwardly projecting shoulder 14. Secured in the inner surface of housing 11 at a point longitudinally disposed from one end of slots 12 is a radially inwardly extending annular ring 15 which defines a valve seat. Ring 15 is sealed to the inner surface of casing 11 by appropriate means, such as the O-ring seal 16.

Body means, such as the valve body 17, is positioned in the tubular casing 11 and generally concentrically oriented therewith. Valve body 17 is also generally tubular in configuration, and may be, for one example, about two inches in length and about inch in diameter. As is clearly viewed in FIGURE 4, the outside surface of the valve body 17 may conveniently be of hexagonal configuration although of course any convenient shape might be employed. As may be clearly viewed in FIGURE 3, valve body 17 may be thought for convenience of explanation to comprise a first portion 18 and a second portion 21 joined together by longitudinally extending ribs 23. Portions 18 and 21 of the valve body 17 may be referred to as the rear portion and front portion, respectively, in view of their positional relationship with the valve seat 15. Likewise, for convenience of reference in explanation, the end of the valve adjacent the seat 15 may be referred to as the downstream end, and the opposite end may be called the upstream end.

Rear portion 18 of valve body 17 includes a radially annular front face 19, and a radially annular rear face 20, said faces being generally perpendicular, of course, to the longitudinal axis of the valve. And owing to its annular shape, this rear portion has both an outer surface, which may conveniently be, for example, cylindrical or hexagonal, and a generally cylindrical inner surface.

Front portion 21 of body 17 also includes a radially annular rear face 22 which is also generally perpendicular to the longitudinal axis of the valve. The downstream end of portion 21 is preferably of slightly reduced diameter to define a valve stem 24, and the outer surface of this valve stem is desirably inwardly tapered or rounded at the downstream extremity thereof to facilitate movement of the valve stem into and out of the valve seat 15. Owing to the generally tubular configuration of the body 17, the valve stem 24 is, of course, annular in cross-section as seen in FIGURE 4, and the inner surface 21a of the portion 21 is a smooth cylindrical surface which may, for example, have a diameter approximately as great as the outer diameter of portion 21.

Extending along the longitudinal axis of valve body 17 and valve chassis 11 and generally concentrically oriented with each said valve body and said chassis is a carrier member such as the central core 25 of generally cylindrical configuration. The longitudinal position of the valve body 17 and the core 25 may each vary independently, within limits, in the chassis 11, but the core 25 will generally extend from a point upstream of the valve body to a point near the face 22 of portion 21 of the valve body.

Securely affixed to central core 25 is a radially outwardly extending thin annular flange 27. The front face of annular flange 27 is adapted to abut face of valve body 17 at times during operation of the valve, as will be explained hereinafter.

Mounted on core intermediate rear portion 18 and front portion 21 of valve member 17 is a stop means, such as the nut 28. The exact position of the nut 28 may be adjusted by suitable means, such as screw 29. At least a portion of nut 28 must extend radially outwardly from core 25 a distance at least as great as the inside diameter of the portion 18 of valve body 17.

It is often desirable to include urging means which will trigger instant or snap action of the valve mechanisms. Such means may conveniently take the form of a coil spring 30 which may be positioned around central core 25 between the rear face of nut 28 and an inwardly extending projection 31 on the inner surface of portion 18 of the valve body. This spring tends to hold the rear face of nut 28 away from the face 19 of rear portion 18 of valve body 17; but, when the spring is compressed, the nut 28 will abut said face 19.

Balancing means, that is, means designed to balance the sensitivity of the valve to tubing pressure on the opening cycle, are associated with the valve body 17. Such means conveniently take the form of balancing piston 33, which is in sliding engagement with the inner cylindrical surface 21a of portion 21 of the valve body. Balancing piston 33 is desirably constructed in the form of a generally solid cylinder 32 having a diameter just slightly smaller than the diameter of the surface 21a. Generally solid cylinder, as used in this connection, includes of course, a cylinder having one solid end face and another end face which is of annular configuration. At the upstream end of the solid cylindrical portion 32 is an outwardly extending oval-like rim or flange 34 preferably having circular ends and flat sides and of sufiicient length along its major axis to permit its circular ends to rest onto the shoulder 14 of casing 11 as depicted in FIGURES 5 and 6. As may further be seen in FIGURE 3, the minor axis of the flange 34 is preferably short enough to permit the balancing piston 33 to pass between the ribs 23 during assembly of the apparatus depicted herein. Since in the gas lift operations, the gas injection conduit pressure is always greater than the tubing pressure, the flange 34- will alway rest on the shoulder 14 during normal operation of the valve. Of course, there is a small axial hole through flange 34 and the adjacent portion of the solid cylinder 32 in order that the end of central core 25 may be slidingly engaged therein. The solid cylinder 32 forms an end face 36 longitudinally opposite the flange 34. Suitable sealing means, such as the O-ring 35, is provided around the outside of portion 32 of the piston 33 to insure sealing engagement as the piston slides along the inside of portion 21. The longitudinal length of the balancing piston 33 is desirably about the same as that of portion 21 of valve body 17. At any rate, this length together with the axial length between portions 18 and 21 of valve body 21, less the axial lengths of the nut 28 and flange 34, is such that at least O-ring seal 35 (and hence the end face 36) of the balancing piston 33 will always be inside the portion 21 of the valve body 17. That is, there can never be flow through the cylindrical passageway defined by the inner surface 21a of portion 21. Of course, it is desirable to include suitable seals, such as the O-ring seal 35, to insure the sealing engagement of these members.

Threadedly joined to central core 25 at threads 26 is a generally solid cylindrical member 38, the downstream end of which is a section of enlarged diameter thus forming an annular shoulder 39. Mounted aroundthe smaller diameter section is a pressure responsive means such as a bellows 40 which is mounted at its other end in any convenient manner as in another section of pipe which is threadedly engaged with the casing 11.

The radial face of the enlarged diameter section of member 38 axially opposite the shoulder 39 is in abutting engagement with the thin annular flange 27. It is thus seen that the flange 27 is axially moved by the pressure differences between the bellows 40 and the downstream end of the valve.

It is readily seen that, when the illustrated valve is employed in a gas lift system, the pressure in the area 45 will always be the gas injection conduit pressure. The pressure in the area 44 will be equal to gas injection conduit pressure when the valve is open, but will be equal to production conduit pressure when the valve is closed.

Valves constructed as above may be conveniently installed in a Well as illustrated in FIGURE 2. Here, the tubing is equipped with a longitudinally extending portion 41 on one side thereof, the portion 41 being of such a size and shape adapted to receive the valve 11. Positioned near the ports or slots 12 in valve 11 is one or more openings 42a in the portion 41. Likewise, near the bottom of the portion 41 is one or more ports 42b in the tubing 5, to afford fluid communication between the valve chamber and the producing conduit. It is usually preferred to include a check valve 43 near the port 42b so that, in case there should be a mechanical failure of some type resulting in reduction of the gas injection conduit pressure below producing conduit pressure, oil in the producing conduit 7 could not escape from that conduit through the valve 11.

OPERATION The operation of the valve in accordance with one embodiment of this invention may be readily understood by reference to FIGURES 5 and 6.

In FIGURE 5, the valve is illustrated in the open position. That is, there is free flow of gas from the exterior of the chassis 11, through the slots 12, through the areas 45 and 44 and thence into the production conduit downstream.

The closing of the valve is governed by the dome pressure, or pressure exerted by the bellows, which is fixed at any desirable value, and the gas injection conduit pressure. The gas injection conduit pressure may be controlled at the surface by means well known to those skilled in the art. Thus, when the gas injection conduit pressure drops sufiiciently so that the pressure (multiplied by its effective area of operation) is less than the dome pressure (multiplied by its effective area of operation), the dome pressure will urge member 38 downstream by virtue of its action on the area of shoulder 39. Core 25, being joined to member 38, will also move axially toward the downstream end of the valve, carrying with it the valve body 17 until the valve stem 24 seats in the ring 15. The valve is thus fully closed, and there is not fluid communication between the gas injection conduit in the area 45 and the producing conduit in the area 44.

It is thus seen that the valve is closed completely independent of the spring 30 and the production conduit pressure.

On Opening, however, the valve is responsive to gas injection conduit pressure, production conduit pressure, and the dome pressure. But even though the opening of the valve is sensitive to tubing pressure, this sensitivity is not great in comparison with the sensitivity of the valve to gas injection conduit pressure. In other words, the opening cycle of the valve is governed to only a very small extent by the pressure in the tubing or production conduit. Specifically, the tubing pressure acts only across an annular area which may be defined as the difference between the area of the seat and the area of the end face 36 of balancing piston 33. The gas injection conduit pressure, meanwhile, acts first across an area defined as the mean effective area of the bellows, and then across an area defined as the difference between the area of the bellows and the annular area defined above in connection with the tubing pressure. This change in the effective area across which the gas injection conduit pressure acts results in a 2-step opening of the valve in normal operating conditions. Since the area of end face 36 may be constructed so as to be relatively large in comparison with the area of the valve seat, it is seen that a valve may be constructed so as to be relatively insensitive to tubing pressure on opening.

When the gas injection conduit pressure acting across the mean effective area of the bellows exceeds the pressure exerted by the dome, plus the force exerted by the spring 30, the member 38 will move axially toward the upstream end of the valve, carrying with it of course the central core 25 and the nut 28 which is secured thereto until the nut 28 abuts the face 19, as illustrated in FIG- URE 6. In this position, the gas injection conduit pressure necessary for further axial movement of the valve in the upstream direction must be such that that pressure, multiplied by the effective area on which it acts (which is now the difference between the area of the bellows and the annular area on which the tubing pressure acts) added to the tubing pressure, multiplied by its effective area, exceeds the force exerted by the dome and the spring 30. When this occurs, the spring 30 will snap the valve body into the open position as shown in FIGURES 3 and 5.

Although the embodiment illustrated and the accompanying discussion has been in terms of a valve which includes an urging means such as the spring 30, and a nut 28, it is recognized that these parts could be eliminated, in which case the valve will have a slightly different operation. That is, instead of the 2-step opening, as discussed above, the valve will go directly from the closed position to the full open position of FIGURE 5 in just one step, without passing through the FIGURE 6 position. In such a case, of course, the gas injection conduit pressure will act at all times across an area defined as the difference between the area of the bellows and the annular area across which the tubing pressure acts. Otherwise, the operation of such a valve will be identical to that discussed above.

EXAMPLE AND PRIOR ART COMPARISON In conventional gas lift valves, the area of the seat governs the sensitivity to tubing pressure on the opening cycle, and the closing cycle is controlled by the gas injection conduit pressure. The operation of such valves on opening are thus governed by the following relationship:

d b c( b s) t s where:

P =Pressure of the dome P =Pressure of the gas injection conduit P =Pressure in the tubing (or production conduit) A =Area of the bellows A =Area of the valve seat.

Thus, if A =0.3 square inch, and A =0.2 square inch, it is seen that the valve is twice as responsive to tubing pressure on opening as it is to gas injection conduit pressure.

Valves constructed in accordance with the present invention, however, are controlled by the following relationship on opening:

where A is the area of end face 36 of the balancing piston. If the areas are the same as given above, and the area of the face 36 is 0.15 square inch (approximately inch diameter), it is seen from the above equation that Or, the valve is five times as sensitive to gas injection conduit pressure as it is to tubing pressure on opening. Expressed in another way, the valve is only 17% sensitive to tubing pressure on opening.

It is thus seen that a valve is provided which is rela tively insensitive to tubing pressure on opening, yet which at the same time provides an adequate throughput capacity to prevent excessive pressure drop across the valve and also provides a streamlined flow path.

While the invention has been described in terms of a particularly preferred embodiment, various changes and modifications may be made herein without departing from the invention, as will be apparent to those skilled in the art.

I claim:

1. -In combination with producing wells and related well flow apparatus comprising:

a well borehole penetrating the earth to a producing formation,

at least one tubing extending into said borehole whereby there is formed within said borehole both at least one producing conduit in fluid communication with said producing formation, and

a gas injection conduit connectable to a source of gas under pressure;

at least one valve mechanism affording fluid communication between said gas injection conduit and said producing conduit and comprising:

an elongated valve housing integral with said tubing and defining a valve chamber therein, said valve housing being so positioned that its longitudinal axis is generally parallel to the longitudinal axis of the tubing;

said housing having a plurality of ports for fluid communication between said gas injection conduit and said producing conduit, and an inwardly projecting shoulder therein;

an annular valve seat mounted in said housing with its face perpendicular to the longitudinal axis of said housing, the inner surface of said valve seat defining an opening for fluid communication between said gas injection conduit and said producing conduit when said seat is open, and fluid isolation between said conduits when said seat is closed;

a central carrier member in said housing extending along the longitudinal axis thereof;

a generally tubular valve body secured to said carrier member and adapted for sliding movement along the longitudinal axis of said housing to thereby alter its axial position relative to each said carrier and said housing;

a portion of said valve body defining an annular valve stem having an inner surface defining a cylindrical passageway through said valve stem, and an outer surface adapted to fit into the inner surface of said valve seat to open and close said valve seat; and

a balancing piston substantially displaced from and not obstructing the major portion of fluid flow through said housing and having a generally solid cylindrical portion having a flange at the upper end thereof, the outer surface of said cylindrical portion being in sliding engagement with the inner surface of said valve stem and positioned to prevent fluid flow at all times through said passageway, and said flange adapted to rest on said inwardly projecting shoulder,

whereby said valve stem is rendered relatively insensitive to tubing pressure on the opening cycle and whereby said valve mechanism is provided with a relatively unobstructed streamlined flow path.

2. A balanced gas lift valve assembly for subsurface interconnection between a production conduit and a gas injection conduit in a well bore, said valve assembly comprising a tubular valve housing having spaced-apart first and second ports for intercommunication with said production and gas injection conduits respectively and further having an inwardly projecting shoulder portion,

a valve seat member disposed in said housing between said first port and said shoulder portion,

a valve body movably disposed in said housing and having a central passageway therethrough and a shutoff surface portion adapted for fluid-tight engagement with said seat member, and

balancing means including a piston member located in said housing in a manner substantially displaced from from and not obstructing the major portion of fluid flow through said housing and having a flange portion at one end adapted to rest on said shoulder portion of said housing and a piston portion slidably and sealingly disposed in said passageway in said valve body to render said valve body relatively insensitive on the opening cycle to fluid pressure in said production conduit.

3. The valve assembly described in claim 2, wherein said valve seat member has an annular configuration with a central aperture for conducting fluid flow from said first port into said housing and with an annular sealing surface located about said aperture and confronting said valve body.

4. The valve assembly described in claim 3, wherein said valve body is movable along the longitudinal axis of said housing, and

wherein said balancing means is a piston member movable along said longitudinal axis of said housing and slidably within said passageway in said valve body.

5. The valve assembly described in claim 4, including a central carrier member movable along the longitudinal axis of said housing, and

wherein said piston member is slidably coupled to said carrier member and disposed between said carrier member and said valve seat member.

References Cited UNITED STATES PATENTS 2,797,700 7/1957 McGoWen 137-155 2,982,226 5/1961 Peters et al 103232 X 3,294,362 12/1966 Schultz et al 251282 X 3,175,514 3/1965 McMurry 137155 X 3,236,493 2/1966 Richards 251283 3,277,838 10/1966 Canalizo 103-1232 DONLEY J. STOCKING, Primary Examiner.

W. J. KRAUSS, Assistant Examiner.

US. Cl. X.R. 137-155 

